EU is one of the major features in the third generation partnership project (3GPP) system. EU offers a peak data rate of 5.76 Mbps. In order to support EU operation, several downlink physical channels, such as an enhanced dedicated channel (E-DCH) absolute grant channel (E-AGCH) and an E-DCH relative grant channel (E-RGCH), are provided to transmit control information.
FIG. 1 is a block diagram of a conventional wireless communication system 100 which supports EU. The system 100 comprises a wireless transmit/receive unit (WTRU) 102, a Node-B 104 and an RNC 106. The RNC 106 controls overall E-DCH operation by configuring E-DCH parameters for the Node-B 104 and the WTRU 102, such as initial transmit power level, maximum allowed transmit power or power ratio, or available channel resources per Node-B. Between the WTRU 102 and the Node-B 104, an E-DCH 108, an E-DCH dedicated physical control channel (E-DPCCH), an E-AGCH 112, an E-RGCH 114 and an E-DCH hybrid automatic repeat request (H-ARQ) indicator channel (E-HICH) 116 are established for supporting E-DCH operations.
For E-DCH transmissions, the WTRU 102 sends scheduling requests, (also known as rate requests), for the logical channels which a radio resource control (RRC) determines that reporting is needed to be made to the Node-B 104 via the E-DCH 108. The scheduling requests are transmitted in the form of scheduling information and a happy bit. The happy bit is transmitted via the E-DPCCH 110 whenever the E-DPCCH 110 is transmitted. The Node-B 104 sends a scheduling grant (i.e., an absolute grant (AG) or a relative grant (RG)) to the WTRU 102 via the E-AGCH 112 or the E-RGCH 114. The AG is sent by an E-DCH serving cell, and the RG is sent by either an E-DCH serving radio link set (RLS) or an E-DCH non-serving radio link (RL). The E-DCH serving cell is a cell from which the WTRU receives AGs from a Node-B scheduler. A WTRU has one E-DCH serving cell. The E-DCH serving RLS is a set of cells which contains at least the E-DCH serving cell and from which the WTRU shall receive an AG. The WTRU has only one serving RLS. The non-serving RL is a cell which belongs to the E-DCH active set but does not belong to the serving RLS and from which the WTRU may receive an RG. The WTRU may have zero, one or several non-serving RL(s).
After E-DCH radio resources are allocated for the WTRU 102, the WTRU 102 transmits uplink data via the E-DCH 108. In response to E-DCH or E-DPCCH transmissions, the Node-B 104 sends an acknowledgement (ACK) or a non-acknowledgement (NACK) message for H-ARQ operation via the E-HICH 116.
The E-AGCH 112 carries an AG which includes an AG value and an activation flag. The AG value is provided in the form of a maximum power ratio for the WTRU. The maximum power ratio is given by the ratio of E-DCH dedicated physical data channel (E-DPDCH) over dedicated physical control channel (DPCCH) power. The activation flag is used to activate or deactivate the H-ARQ processes. The activation flag may be set to either “SINGLE” or “ALL.” If the activation flag is set to “SINGLE”, a single H-ARQ process is activated or deactivated. If the activation flag is set to “ALL”, all H-ARQ processes are activated or deactivated.
The E-RGCH 114 carries an RG. The RG indicates power (or power ratio) up or down commands to adjust the absolute grant. The serving RLS may send UP, DOWN or HOLD commands and the non-serving RL may send DOWN or HOLD commands. The UP, DOWN or HOLD commands indicate an increase, decrease or no change of the maximum allowed power ratio of the WTRU for the scheduled transmission of data, respectively. The commands from different non-serving RLs are independent and may be different from one another. The E-DCH non-serving RLs send the RG to prevent system overloading in data traffic and maintain the intra-cell and inter-cell interference at the required level.
A network may control single WTRU or a group of WTRUs via the E-AGCH, the E-RGCH, or both. When in a primary AG mode, the Node-B controls the resource scheduling for only a particular WTRU via the E-AGCH. When in a secondary AG mode, the Node-B controls the resource scheduling for a group of WTRUs via the E-AGCH. The E-AGCH is transmitted with an E-DCH radio network temporary identifier (E-RNTI). Two E-RNTIs may be configured for the WTRU at a time. One is a primary E-RNTI and the other is a secondary E-RNTI. Only one E-RNTI may be transmitted in the air at a time. The WTRU should monitor both E-RNTIs if the WTRU is configured with both E-RNTIs.
The WTRU calculates and sets a serving grant (SG) based on the received AG and RG. A successful detection and decoding of the E-AGCH 112 and the E-RGCH 114 and proper setting of the SG are important for the performance of systems and the performance of EU. Therefore, it is desirable to have a method and apparatus for efficiently detecting and decoding the AG and RGs and processing the SG.